US20200029975A1 - Automatic tourniquet for emergency or surgery - Google Patents

Automatic tourniquet for emergency or surgery Download PDF

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Publication number
US20200029975A1
US20200029975A1 US16/469,239 US201716469239A US2020029975A1 US 20200029975 A1 US20200029975 A1 US 20200029975A1 US 201716469239 A US201716469239 A US 201716469239A US 2020029975 A1 US2020029975 A1 US 2020029975A1
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Prior art keywords
pressure
tourniquet
limb
inflatable
circumference
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Abandoned
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US16/469,239
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English (en)
Inventor
Adam Jones
Kiran Hamilton J. Dellimore
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Koninklijke Philips NV
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Koninklijke Philips NV
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Priority to US16/469,239 priority Critical patent/US20200029975A1/en
Publication of US20200029975A1 publication Critical patent/US20200029975A1/en
Abandoned legal-status Critical Current

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/12—Surgical instruments, devices or methods, e.g. tourniquets for ligaturing or otherwise compressing tubular parts of the body, e.g. blood vessels, umbilical cord
    • A61B17/132—Tourniquets
    • A61B17/135—Tourniquets inflatable
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B17/12—Surgical instruments, devices or methods, e.g. tourniquets for ligaturing or otherwise compressing tubular parts of the body, e.g. blood vessels, umbilical cord
    • A61B17/132—Tourniquets
    • A61B17/135—Tourniquets inflatable
    • A61B17/1355—Automated control means therefor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/021—Measuring pressure in heart or blood vessels
    • A61B5/022—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/107—Measuring physical dimensions, e.g. size of the entire body or parts thereof
    • A61B5/1072—Measuring physical dimensions, e.g. size of the entire body or parts thereof measuring distances on the body, e.g. measuring length, height or thickness
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B2017/00017—Electrical control of surgical instruments
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B2017/00017—Electrical control of surgical instruments
    • A61B2017/00022—Sensing or detecting at the treatment site
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B2017/00017—Electrical control of surgical instruments
    • A61B2017/00022—Sensing or detecting at the treatment site
    • A61B2017/00026—Conductivity or impedance, e.g. of tissue
    • A61B2017/0003—Conductivity or impedance, e.g. of tissue of parts of the instruments
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B2017/00017—Electrical control of surgical instruments
    • A61B2017/00115—Electrical control of surgical instruments with audible or visual output
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
    • A61B2017/00681—Aspects not otherwise provided for
    • A61B2017/00734—Aspects not otherwise provided for battery operated
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A61B2090/061—Measuring instruments not otherwise provided for for measuring dimensions, e.g. length
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A61B2090/064—Measuring instruments not otherwise provided for for measuring force, pressure or mechanical tension
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
    • A61B2560/02—Operational features
    • A61B2560/0204—Operational features of power management
    • A61B2560/0214—Operational features of power management of power generation or supply

Definitions

  • the invention relates to medical devices. Specifically, to the field of tourniquet devices with the aim of reducing blood flow to a limb of a person or an animal. Especially tourniquet devices for preventing hemorrhage due to injuries or for reducing blood flow during surgery. More specifically, the invention provides a method and a tourniquet device for automatic blood occlusion of limb.
  • Tourniquets are effective devices in the treatment of blast wounds, penetrating trauma (such as stab wounds or gunshots), industrial accidents and injuries sustained in remote, resource scarce environments, where more comprehensive medical attention is not immediately available.
  • tourniquets are applied with no readout or feedback whatsoever regarding the tourniquet pressure, meaning that it may be far in excess of the minimum required pressure, or perhaps even insufficient to provide full occlusion.
  • Tourniquets are also commonly used in surgical applications to reduce blood flow to an extremity. It is an effective method of improving the quality of the surgical field, affording the surgeon a bloodless area of operation.
  • Surgical tourniquets are most often pneumatic, electrically-powered and include some form of pressure sensor.
  • the exact pressure required to occlude venous and arterial blood flow beneath the tourniquet is dependent on the blood pressure of the patient, the dimensions of the anatomical site where it is applied and the characteristics of the compressed soft tissue.
  • surgical tourniquets are often applied at an arbitrary pressure of the surgeon's choosing, which is known to prevent blood flow but is also likely to be excessively high and risk damage to the underlying tissue.
  • the ‘gold standard’ procedure which is typically followed when the tourniquet is correctly applied, is outlined as follows: a dedicated tourniquet must be used, since improvised devices often take too long to fabricate and their inefficiency may cause complications for the patient.
  • the tourniquet is placed just above the wound and tightened (by a pump, windlass or some other mechanical means) until the circumferential pressure is sufficient to completely occlude arterial and venous blood flow.
  • the time of application is recorded and submitted to the receiving hospital. It is sometimes advised that the time of application is written on the patient's forehead (or another easily visible location) to minimise the risk of the compression time going unrecorded and exceeding the recommended maximum duration of one hour. If transit time is less than an hour, the device will typically be left in place until the patient enters the operating theatre. For longer transit times and if the patient is stable, it may be possible to loosen the tourniquet as long as bleeding is fully controlled.
  • the invention provides an inflatable tourniquet system for arterial blood occlusion of a limb, the system comprising
  • Such tourniquet system is advantageous, since it provides a simple procedure to be followed by an untrained user for obtaining a pressure which is high enough to ensure arterial blood occlusion, and which is yet low enough to be safe with respect to tissue damage. This is obtained with the feedback provided to the user, e.g. light, sound, text, when the user has manually inflated the inflatable chamber to an appropriate pressure level.
  • a target pressure can be calculated from a measured SBP and and estimated tissue padding coefficient (TPC) which can be calculated from the circumference of the limb, and that this circumference can be measured along with the user fastening the tourniquet, e.g. by measuring electric resistance in a conductor of the tourniquet, once fastened around the limb.
  • TPC tissue padding coefficient
  • the target pressure calculation can be performed automatically, and the procedure can be performed quickly by an untrained user, and this helps to reduce the time before the user can apply sufficient pressure to stop the bleeding. Still further, the fact that feedback is given to the user, the user will not be afraid of incidentally applying a too high pressure, and thus the user will not hesitate to perform the manual inflation in a quick manner.
  • the system only demands a small amount of electric power to drive the processor, the blood pressure meter circuit and the electric circuit used to measure resistance.
  • a small battery e.g. a rechargeable battery to be powered by the manual inflator.
  • the system may comprise an automatic inflator or pump to inflate the inflatable chamber of the tourniquet to the target pressure, i.e. removing the need for manual inflation, after the target pressure is determined.
  • the system could also automatically maintain this pressure for a prescribed safe amount of time. This requires an electric power source to power the automatic inflator of pump.
  • the processor is preferably arranged to calculate the target pressure as a sum of a first value representing the measure of systolic blood pressure using (SBP) and a second value calculated in response to said electrical resistance of said part of the conductor corresponding to a circumference of a limb.
  • the target pressure calculated is an estimation of the Arterial Occlusion Pressure (AOP), which is the lowest pneumatic tourniquet inflation pressure required to stop arterial blood flow into the limb, and its usage has been shown to be useful in optimizing tourniquet cuff pressures.
  • AOP Arterial Occlusion Pressure
  • the AOP can be estimated from the SBP and the Tissue Padding Coefficient (TPC), which is based on the circumference of the limb before cuff inflation as follows:
  • the Tissue Padding Coefficient is based on the circumference of the limb before cuff inflation, and thus TPC can be estimated in response to the measured resistance of the electric conductor, e.g. by means of a prestored look-up table.
  • the calculation of target pressure preferably involves calculating a value indicative of TPC of the limb in response to the electrical resistance of the part of the conductor corresponding to a circumference of a limb, and a value from a prestored table.
  • a margin for error of such as 20 mmHG may be added to the AOP yielding the following expression for target pressure, i.e. optimal AOP (OAOP):
  • a target pressure interval can be determined based on the calculated target pressure, e.g. OAOP.
  • the processor may be arranged to control the feedback device to provide at least three different types of feedback to the user in response to input from the pressure sensor, so as to indicate whether the pressure is: below, within, or above the calculated target pressure interval, respectively.
  • the user can: inflate further, stop inflation, or activate a deflation valve, respectively.
  • the feedback device may comprise at least a visual indicator or an audible indicator, or a combination of both.
  • a visual indicator may provide a feedback signal by means of coloured lights, e.g. LEDs, a black white or color display (e.g., low power e-ink screen) to show text and/or symbols.
  • an audible indicator may provide different audible tones, and/or speech to guide the user.
  • the electrical conductor is mounted in a lining of the tourniquet.
  • the electrical circuit is preferably connected to the electrical conductor, so as to allow electrical contact with respective ends of the part of the electrical conductor which corresponds to a circumference of the limb.
  • the electric conductor is preferably arranged along the length of the tourniquet, and wherein the fastening mechanism is used to provide electric connection to a part of the electric conductor which corresponds to the circumference of the limb, thereby allowing the measuring resistance to reflect the circumference of the limb.
  • the processor can then receive a resistance value from the electric circuit, e.g. when the pressure sensor indicates that inflation has started.
  • the measurement of electrical resistance is based on the principle that the resistance of a conductive wire changes with geometry, which is commonly utilized in strain gauges.
  • the lateral and/or axial strain can therefore be correlated to the diameter of the limb.
  • a smaller diameter limb should therefore correspond to a higher strain than a large diameter limb.
  • the conductive wire is preferably integrated or built into a sleeve of the tourniquet, such that it can measure the lateral strain as it is wrapped around the limb.
  • the electric conductor may have a zig-zag or square wave pattern of parallel lines in order to ensure that a small amount of stress in the direction of the orientation of the parallel lines results in a multiplicatively larger strain measurement over the effective length of the electric conductor.
  • the manual inflator preferably comprises a bulb inflator arranged for being squeezed by the user in order to inflate the inflatable chamber.
  • the manual inflator may be provided by means of a rotationally activated pump.
  • the system may comprise a clock arranged to determine a time of application of the tourniquet on the limb, and wherein the system is arranged to provide a feedback in response to said time of application of the tourniquet.
  • the E.g. the clock may be set to determine the time of application of the tourniquet on the limb to the time, where the processor receives a sensed pressure from the pressure sensor which exceeds a preset value.
  • a small e-ink screen and a real time clock are incorporated into the system, which together will display the time since the optimal tourniquet (or target) pressure was first achieved or alternatively a countdown from the maximum permitted tourniquet application time, e.g. one hour.
  • An alarm, buzzer or flashing light may also be added, which will be activated when the maximum application time is approached and also when the tourniquet pressure falls out of the optimal range.
  • the system comprises an mechanical energy harvesting device arranged to generate electric energy to power at least the processor in response to manual operation of the manual inflator, e.g. all of the electric power demanding elements of the system may be powered by the mechanical energy harvesting device.
  • the system can function also in locations, where no electric power outlet or replacement batteries are available.
  • the system may comprise an electric energy storage element arranged to store electric energy generated by the electric energy harvesting device.
  • the energy harvesting device may comprise a manual inflator in the form of a bulb, where a linear alternator is used to harvest electric energy from the pumping action of the bulb, which could then be used to power some or all of the device's electronic functionality.
  • a linear alternator can be used to directly convert the linear motion of the compression/squeezing of the bulb and handle during inflation into electrical energy.
  • a rotary alternator can be used if the handle is linked via a crank or step-up gear to a rotatable flywheel (e.g., flywheel magnet rotor) connected to a dynamo with a commutator (necessary for rectification of the alternating current to direct current-since).
  • a linear alternator may be preferred in order to make the device more compact and less bulky, however, a small rotary alternator may also be used.
  • energy could be harvested from the drawing of tourniquet material through an external housing using a rotary alternator.
  • the amount of energy stored in a (super-) capacitor could then be measured, giving information about the amount of fabric which has been drawn through the housing, thus providing a measurement of the length of tourniquet remaining around the limb and thereby indicating a measurement of limb circumference. In this way energy harvesting and measurement of a value indicative of limb circumference can be combined.
  • the processor may be arranged inside a casing attached to a part of the tourniquet.
  • the processor may be arranged in a stand-alone device, e.g. inside a separate casing housing the blood pressure measuring circuit.
  • the tourniquet system of the first aspect is applicable to trained as well as untrained users to emergency or other situations where arterial occlusion of a limb is advantageous, also as part of first aid kits to be used at places without any access to electric energy sources.
  • this invention will help to reduce the time of application of tourniquets, reduce the occurrence pressure-related injuries and make tourniquets more accessible to inexperienced and low-skilled users in emergency situations.
  • the electric circuit arranged to measure an electrical input from a length sensor and to determine a value indicative of circumference of the limb accordingly, can be implemented in various ways apart from the mentioned embodiment with measuring electrical resistance of an electric conductor.
  • the limb circumference may be measured using a rotating element of a known circumference placed within the an external housing of the tourniquet.
  • This rotating element will be rotated by the tourniquet material, as it is drawn through the housing and as each full rotation is completed, a counter increases in value. If the element has a circumference of say 1 cm, 20 rotations would therefore be recorded by the counter, indicating that 20 cm of material had been drawn through the housing.
  • the amount of fabric which has been drawn through the housing thus provides a measurement of the length of the tourniquet remaining around the limb and thereby indicates a measurement of the limb circumference.
  • the limb circumference may be measured using a capacitive linear encoder, similar to those found in digital Vernier calipers. Two patterns of bars with a known separation are printed on both the tourniquet material and on the circuitry within an external housing of the tourniquet. The measured capacitance changes as the material slides through the housing, counting the number of printed bars which have passed through, thereby arriving at a measure of circumference of the limb.
  • the limb circumference may be measured using a capacitive measurement of tourniquet material which has been drawn through an external housing of the tourniquet.
  • the capacitance reveals the amount of fabric which has been drawn through, which in turn reveals what length of material remains around the limb, thereby reflecting limb circumference.
  • the invention provides a method for determining feedback to a user of an inflatable tourniquet for arterial blood pressure occlusion of a limb, the method comprising
  • the invention provides a computer program product comprising computer readable program code which, when executed on a processor, causes the processor to perform the method according to the second aspect.
  • the program code may be present on a tangible medium, e.g. a memory card or the like, a read only memory, or it may be present on a server for downloading via the internet.
  • the processor preferably has a connected memory for performing calculations, and also a memory for storing the program code to be executed.
  • FIG. 1 illustrates a sketch of elements of an inflatable tourniquet system
  • FIG. 2 illustrates steps of a method embodiment.
  • FIG. 1 shows an inflatable tourniquet system embodiment.
  • the system is suitable for arterial blood occlusion of a limb, and it is suitable in emergency situations where even untrained users can operate the system, e.g. to provide a fast helping action to stop a bleeding from an injured limb.
  • the system has a tourniquet TQ arranged to be manually fastened around a limb by a user.
  • the tourniquet TQ has a built in inflatable chamber CH in connection with a manual inflator B, e.g. a squeezable bulb, so as to allow application of a pressure for occlusion of arterial blood flow to the limb, upon inflation of the inflatable chamber by manually operating the manual inflator B.
  • the inflatable tourniquet TQ may be similar to those known in the art with respect to its structure, size and closing mechanism etc.
  • the tourniquet TQ has an electric conductor C arranged in or on its structure, which allows measurement of an electrical resistance R of a part of the electric conductor C corresponding to a circumference of a limb, when the tourniquet TQ has been fastened around the limb.
  • the electric conductor C may be formed by e.g. copper, aluminium, steel, or other conducting material with known resistivity, preferably the electric conductor C is provided inside an insulating material.
  • the electric conductor C is a wire.
  • the electric conductor C is connected to an electric circuit CC which can generate a measure of the electrical resistance R of the part of the electric conductor C corresponding to a circumference of the limb.
  • the electrical circuit CC is connected to the electrical conductor C, so as to allow electrical contact with respective ends of the part of the electrical conductor which corresponds to a circumference of the limb.
  • the electric conductor C can be arranged along the length of the tourniquet TQ, and wherein the fastening mechanism of the tourniquet TQ (not shown) is used to provide electric connection to a part of the electric conductor C which corresponds to the circumference of the limb, thereby allowing the measuring resistance to reflect the circumference of the limb.
  • the electric conductor C is shown to have a zig-zag or square wave pattern with conducting parts parallel with a length direction of the tourniquet, so as to indicate a preferred type of electric conductor C which allows measuring an electric resistance value varying with lateral strain as the tourniquet TQ is wrapped around the limb.
  • the electric conductor C in accordance with the principle of a strain gauge.
  • the electric conductor C may be mounted, e.g. integrated, in a sleeve of the tourniquet TQ.
  • a blood pressure measuring circuit BP is arranged to automatically determine a measure of a systolic blood pressure SBP in response to input from a pressure sensor PS arranged to measure a pressure of the inflatable chamber CH.
  • Such automatic blood pressure measuring circuit BP is known in the art, e.g. it may operate according to an oscillometric method as known in the art.
  • the blood pressure measuring circuit may start operating once the pressure sensor PS senses a pressure exceeding a preset value.
  • a feedback device FBD serves to provide a feedback FB to the user, e.g. a visible and/or audible feedback.
  • the feedback device FBD may comprise an LED array or a similar arrangement to provide feedback FB to the user applying the tourniquet and indicate when the tourniquet pressure is above, below or within the optimal range.
  • a processor P or preferably a processor system including memory etc., is arranged for connection to the blood pressure measuring circuit BP, the pressure sensor PS, the electric circuit CC, and the feedback device FBD.
  • the processor P is programmed to operate according to a control algorithm, preferable with its executable program code stored in read-only memory.
  • the control algorithm serves:
  • the target pressure is preferably calculated as in Eq. (1) or (2) as further explained below.
  • the user is provided with feedback FB about the manual inflation process and can thus stop further inflation, once the target pressure has been obtained.
  • the manually operated tourniquet is tightened around the extremity, i.e. limb (arm or leg), by drawing the tourniquet material through an external housing until the limb is tightly encircled.
  • the cuff of the tourniquet is then locked in place using a clamp on the tourniquet housing unit.
  • the manual inflator bulb is squeezed, and the inflation chamber of the cuff begins to inflate.
  • the electrical resistance of the loop is measured and from this the length of wire can be calculated, using known resistivity and diameter values for the wire.
  • the tourniquet is inflated manually by the user up to a pressure above SBP.
  • An SBP measuresment can only be taken after inflation is complete, and during deflation of the inflatable chamber after a pressure above SBP has been achieved.
  • the tourniquet is then be inflated again to inflate it to the target pressure, i.e. preferably Arterial Occlusion Pressure (AOP) or Optimal AOP (OAOP).
  • a safety margin of 20 mm HG is added. This safety margin may be chosen to be smaller or larger than 20 mmHG, e.g. it may be selected in the range 10 mmHG to 50 mmHG.
  • the CPU chip compares the pressure of the tourniquet with the optimal pressure and will give feedback to the user, to guide the user into bringing the tourniquet within the optimal pressure range. This is achieved, for example, using a red LED to signal that the tourniquet pressure is too low, green LED to signal that the pressure is correct and a flashing orange or blue LED to alert nearby emergency operators that the tourniquet pressure has risen above the optimal level. Alternatively, or additionally, feedback may be given to the user by means of a small screen e.g. an e-ink screen.
  • the user receives positive feedback from the system and will stop squeezing the bulb.
  • SBP is preferably automatically measured at regular intervals (e.g. every 5 minutes) to check for changes in the patient's blood pressure.
  • the calculations of AOP and OAOP are automatically repeated each time, using the original limb circumference reading for the calculation. This method allows the system to ignore changes in limb circumference caused by the pressure of the tourniquet. If the SBP has changed such that the tourniquet pressure is now outside the optimal range, feedback will once again be given to the user to adjust the tourniquet application pressure until it falls again in the optimal range.
  • the energy available to harvest from either of the mentioned methods would likely be sufficient to record data for tourniquet pressure, limb circumference etc. and to then make calculations and provide user feedback with this data.
  • FIG. 2 shows steps of an embodiment of a method for determining feedback to a user of an inflatable tourniquet for arterial blood pressure occlusion of a limb.
  • the method comprises an initial step of inflating I_TQ the inflatable chamber of the tourniquet. By sensing that the pressure in the inflatable chamber has reached a preset minimum pressure value, the further steps can be initiated. This inflation is done by the user.
  • the further steps include receiving R_R a value indicative of electrical resistance of a part of an electric conductor arranged in the tourniquet, when the tourniquet has been fastened around the limb, wherein the part of the conductor corresponds to a circumference of the limb.
  • the method comprises receiving R_SBP a value indicative of SBP determined in response to a pressure measured in an inflatable chamber of the inflatable tourniquet. Further, the method comprises calculating a target pressure C_TPR in response to the value indicative of SBP, and the electrical resistance of the part of the conductor corresponding to a circumference of the limb. Preferably, a targer pressure interval is calculated. Still further, the method comprises monitoring pressure MN_PR of the inflatable chamber and comparing the pressure of the inflatable chamber of the tourniquet with the calculated target pressure, and providing feedback P_FB to the user, indicating that the pressure of the inflatable chamber has reached the calculated target pressure.
  • the invention provides an inflatable tourniquet system for arterial blood occlusion of a leg or arm, e.g. after injury or for surgery.
  • a tourniquet TQ is to be manually fastened around the limb by a user, e.g. a first aid helper, e.g. an untrained person.
  • a manual inflator B is used to inflatable the tourniquet to apply pressure for occlusion of arterial blood flow to the limb.
  • An electric circuit CC measures an electrical input from a length sensor C, e.g. an electric conductor, and to determine a value R, e.g. electric resistance, indicative of circumference of the limb accordingly, when the tourniquet has been fastened around the limb.
  • a blood pressure measuring circuit BP automatically determines a systolic blood pressure SBP in response to input from a pressure sensor PS arranged to measure a pressure PR of the tourniquet.
  • a processor P is programmed to operate according to a control algorithm which calculates a target pressure in response to the measured SBP, and the value R indicative of circumference of the limb. Then, the processor monitors input from the pressure sensor PS and compares the sensed pressure with the calculated target pressure. Visual and/or audible feedback is give to the user, when the pressure of the tourniquet TQ is within an interval of the target pressure.
  • the manual inflator B process may be used to provide energy harvesting for electric powering the system.
  • a computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

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US16/469,239 2016-12-13 2017-12-12 Automatic tourniquet for emergency or surgery Abandoned US20200029975A1 (en)

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CN111481253B (zh) * 2020-03-26 2022-08-02 刘夙璇 一种气囊式动脉压迫止血控制系统及其配套设备
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